A conventional electronic component feeder is explained referring to FIGS. 9 to 15.
Such an electronic component feeder is commonly designed for supplying electronic components 1 from an electronic component carrying tape A shown in FIG. 9. This is not only because components 1 can be aligned in a row which is advantageous for continuous supply but also because such tape allows easy conveying and handling by an operator.
The electronic component carrying tape A shown in FIG. 9 includes a holder tape 3 having a row of storage recesses 2 provided therein at equal intervals in a lengthwise direction, the electronic components 1 stored in their respective storage recesses 2, a top tape 4 attached to the upper surface of the holder tape 3 for protecting and preventing electronic components 1 from dropping off, and a row of sprocket apertures 5 provided at equal intervals in a lengthwise direction.
For supplying the electronic components 1 from the electronic component carrying tape A, it is necessary to repeat a cycle of actions comprising three steps; peeling off the top tape 4, holding the electronic component 1 with a suction nozzle, and advancing the electronic component carrying tape A by a distance equal to the distance between any two adjacent storage recesses 2.
Such cycle of actions carried out in a conventional electronic component feeder installed in an electronic component mounting apparatus will now be described in more detail referring to FIGS. 10 to 15.
Motions of each element of the component feeder in accordance with actions of the suction nozzle will be described according to the timing chart shown in FIG. 13 as well as referring to the front view in FIG. 10, the rear view in FIG. 11, and the plan and cross sectional views of a tip of the component feeder in FIG. 12.
As shown in FIG. 13, each element repeats component feeding actions in accordance with a cycle of actions consisting of descending, attracting components by suction, and ascending of the suction nozzle in the electronic component mounting apparatus.
Referring to FIGS. 10 to 12, in response to the actions of the suction nozzle, an actuator lever (not shown) comes into contact with a feed lever 6 (denoted by oblique lines in FIG. 10) which then turns down clockwise about a first pivot center 16 as shown in FIG. 10. As the feed lever 6 has turned down a given distance, it strikes a take-up lever 11 which then turns up clockwise as shown in FIG. 10.
One cycle of actions the feed lever 6 which consists of descending, pausing, and ascending is converted by a link 7 to the forward and backward turning motion of a wheel driving lever 18 about a second pivot center 19.
Through a combination of a first pin 20 fitted into a hole 24a of a shutter 24 mounted to the wheel driving lever 18, second pins 22, 22 mounted to the tape guide 12, and a slot 23 provided in the shutter 24 for engagement with and guidance of the two second pins 22, the forward and backward turning action of the wheel driving lever 18 is converted to an intermittent linear reciprocating movement of the shutter 24. The shutter 24 has a distal end 24b bent down as best shown in FIGS. 12A and 12B so that it can reciprocate intermittently on the tape guide 12 without covering the entirety of a suction window 25 provided at a component pick-up position of the tape guide 12 but holding a central position of the electronic component 1 exposed to the suction window 25. The distal end 24b of the shutter 24 remains retracted in a gap 24a defined in the tape guide 12 when the suction window 25 is not closed with the shutter 24.
Accordingly, as shown in FIGS. 11 to 13, when the feed lever 6 is started to turn downwardly, the shutter 24 moves backward to the right-hand side in FIG. 11, allowing the distal end 24b thereof to retreat into the gap 24a. As the actuator lever in the electronic component mounting apparatus stops at its given position, the turning movement of the feed lever 6 is ceased thus to halt the take-up lever 11 and the shutter 24. Since the shutter 24 is at this time in its retracted position, the suction window 25 of the tape guide 12 is fully opened.
The suction window 25 has a larger opening area than for picking up the component 1. When the suction window 25 is open, the electronic component 1 is located substantially at the center of the suction window 25.
The suction nozzle which has been lifted down then picks up the electronic component 1 and moves upward.
The upward movement of the suction nozzle triggers an upward turning action of the actuator lever of the electronic component mounting apparatus. The feed lever 6 accompanies the upward motion of the actuator lever by the function of a return spring 9 and turns counterclockwise about the first pivot center 16 in FIG. 10. As the feed lever 6 turns upward, it departs from the take-up lever 11 which is thus driven by the pulling force of a return spring 10 to descend counterclockwise in FIG. 10.
The take-up lever 11 and the reel 8 are mounted on a common axis about the first pivot center 16 and provided with a known one-directional rotary ratchet mechanism. As shown in FIG. 10, the counterclockwise turning of the take-up lever 11 directs the counterclockwise turning of the reel 8. When the take-up lever 11 is turned clockwise, the one-directional rotary ratchet mechanism causes the reel 8 to rest. Accordingly, the pulling force of the return spring 10 exerted on the take-up lever 11 becomes a force for turning the reel 8 counterclockwise and thus a force for taking up the top tape 4. The top tape 4 is peeled off from the upper surface of the holder tape 3 by this force at the slit 13 of the tape guide 12 when the electronic component carrying tape A is conveyed in the direction denoted by the arrow in FIG. 10 and taken up via a stationary roller 15 around the reel 8.
Simultaneously, the wheel driving lever 18 turns counterclockwise in FIG. 11 about the second pivot center 19 and its turning drives the shutter 24 to move to the left-hand side in FIG. 12A and close the suction window 25.
The wheel driving lever 18 and a wheel 21 turn about the common second pivot center 19 and are provided with a known one-directional rotary ratchet mechanism between them. Only when the wheel driving lever 18 turns counterclockwise in FIG. 11, the wheel 21 is rotated in the same direction together with the lever 18. The wheel 21 has a plurality of pins 21a provided at equal intervals of a pitch on the circumference thereof for engagement with the sprocket apertures 5 of the holder tape 3. With the forward movement of the shutter 24 to the left-hand side in FIG. 12A the wheel 21 turns counterclockwise FIG. 11, the pins 21a at its circumferential edge engaging with the sprocket apertures 5 of the holder tape 3, thereby driving the holder tape 3 in the turning direction of the wheel 21.
At this time, the top tape 4 which has been urged by the peeling force departs from the upper surface of the holder tape 3 as shown in FIG. 10 and is taken up by the reel 8 via the stationary roller 15. As the feed lever 6 stops at its upper limit, the wheel driving lever 18 comes to a halt, and so do the shutter 24 and the electronic component carrying tape A.
When the reel 8 has taken up the top tape 4, its action stops upon the tension on the top tape 4 being balanced with the take-up force. At the time of completing its action, the take-up lever 11 rests at the position away from the feed lever 6 and remains urged counterclockwise in FIG. 10 by the yielding force of the return spring 10. Such resting position of the take-up reel 11 is varied depending on the taken-up quantity of the top tape 4 on the reel 8, i.e, the diameter of the taken-up tape.
FIG. 14 illustrates a holding member 14 for elastically holding down the tape guide 12 onto a feeder body 17. While the electronic component carrying tape A conveys the electronic components 1 stored in their respective recesses 2 of its holder tape 3 and held under the top tape 4 as mentioned above, the tape guide 12 assists the electronic components 1 to stay in their respective recesses 2 before the electronic components 1 are picked up by the suction nozzle after removal of the top tape 4. Also, the tape guide 12 prevents the electronic component carrying tape A from lifting up, loosening, or displacing upon the top tape 4 being peeled off. The holding member 14 is pivotally supported by a pivot 14b and urged by a spring 26 to inhibit the lifting motion of the tape guide 12.
As shown in FIG. 10, the actuator lever of the electronic component mounting apparatus travels two, large and small, distances d and c to strike and cause the feed lever 6 to descend clockwise in FIG. 10 about the first pivot center 16. There are hence provided two types of electronic component feeder for allowing the feed lever 6 to move a small stroke c' in response to a motion of the actuator lever by the small distance c and a large stroke d' in response to a motion of the actuator lever by the large distance d.
In the former type of electronic component feeder in which the feed lever 6 moves a smaller stroke c', the feed lever 6 is constructed such as to be able to move the large stroke d' so that it can follow an erroneous motion by the large distance d of the actuator lever for preventing any damage of the electronic component feeder.
As explained, the conventional electronic component feeder allows the take-up lever 11 to be turned counterclockwise in FIG. 10 in response to the returning motion of the feed lever 6 thus rotating the reel 8 in the same or take-up direction to take up the top tape 4. The angle of rotation of the reel 8 and the take-up lever 11 varies depending on the amount of taken up top tape 4 on the reel 8. When the diameter of the taken up quantity of the top tape 4 is small, the angle of rotation is large. If the diameter of the taken up quantity is large, the angle of rotation is small. Since the angle of rotation is not constant, the feed lever 6 and the take-up lever 11 which are detachable from each other turn together in an early stage of the motion, where the feed lever 6 turns counterclockwise in FIG. 10 and the take-up lever 11 turns in the same direction. Upon the top tape 4 having been taken up, the take-up lever 11 stops its motion and the feed lever 6 continues its turning motion to depart from the take-up lever 11 before coming to a halt as shown in FIG. 15A.
As the feed lever 6 turns in the forward direction, it travels clockwise in FIG. 10 and FIG. 15A, hits against a contact point 28 of the take-up lever 11 on its way, and further moves together with the take-up lever 11 in the clockwise direction. As previously mentioned, the take-up lever 11 rotates clockwise in FIG. 10 freely from the reel 8 which is pausing.
Such hitting occurs when the shutter 24 is at its retracted position as shown in FIG. 13. In other words, the strike occurs at a moment just before the suction window 25 is opened. Hence, the impact or vibration generated by at the striking may shake the electronic component 1 held without any protecting force and located in the center of the opened suction window 25 and if worse, allow it to jump out from the storage recess 2 or turn to a vertical state. Minute electronic components 1 are more liable to be affected by such impact or vibration especially as the speed of mounting operation is increased, which causes a decline in the picking up capability of the suction nozzle.
As shown in FIG. 14, the tape guide 12 and the holding member 14 are contacted with each other at a point 27 where an extension 12a of the tape guide 12 touches a projection 14a of the holding member 14. However, such structure does not allow the holding member 14 and the tape guide 12 to smoothly contact with each other at the contact point 27, and the force of the spring 26 for holding down the tape guide 12 is not efficiently transmitted thereto.
When the tape guide 12 is lifted up from the electronic component carrying tape A for some reasons such that the suction nozzle fails to pick up the electronic component 1 or that the electronic component 1 drops down between the holder tape 3 and the tape guide 12, the force of the spring 26 for holding down the tape guide 12 cannot swiftly follow up because of the poor condition of smoothness at the contact point 27. Accordingly, a gap beneath the tape guide 12 will not be eliminated immediately even after the electronic component 1 has been removed out by the advancing movement of the tape A. The electronic components 1 locating between a position where the top tape 4 has been peeled off and a pick-up position thus lose the holding down force above them, by which their postures may be disturbed thus lowering the efficiency of picking up action.
In the electronic component feeder in which the feed lever 6 moves the small stroke c', the feed lever 6 is constructed to be able to move the large stroke d' in order to prevent any damage in the event that the actuator lever of the electronic component mounting apparatus moves the large stroke d erroneously. This causes such problem as described below. When setting the electronic component carrying tape A into the electronic component feeder with the small stroke c', the feed lever 6 is manually moved. It is, however, difficult to cause the feed lever 6 to move precisely by the stroke c' and stop there. In case that the feed lever 6 is moved further from the small stroke c', the electronic component carrying tape A travels an excessive distance hence releasing two or more of the electronic components 1 at once and producing a loss. In addition, the peeling off of top tape 4 is interrupted on the way and the top tape 4 may be conveyed together with the holder tape 3 and stuck between the tape guide 12 and the feeder body 17.
When the actuator lever in the electronic component feeder designed for the small stroke c' mounted in electronic component mounting apparatus is moved accidentally by the large stroke d due to setting errors of the program, the feed lever 6 is returned by the large stroke d' to its initial position in the counterclockwise direction. This will delay the identification of such setting errors in the program of the electronic component mounting apparatus. Also, the amount of movement of the shutter 24 is increased, causing a critical collision between the shutter 24 and the suction nozzle.